1. Field of the Invention
The present invention relates to a reflective liquid crystal display device which does not need a backlight, and a method for manufacturing the same.
2. Description of the Prior Art
In recent years, applications of liquid crystal display devices to word processors, lap-top personal computers, pocket-size TV displays, and the like have been in rapid progress. Especially, a reflective liquid crystal display device in which incident light is reflected to effect a display eliminates the necessity of any backlight, thereby lowering power consumption as well as reducing the size and the weight of the device.
The conventional liquid crystal display devices mostly employ a twisted nematic (TN) mode or a super-twisted nematic (STN) mode. In such display devices, about a half of the natural light introduced therein is absorbed, not being reflected to the outside by a linear polarizer disposed therein, resulting in a dark display. To overcome this trouble, other display modes have been proposed in an attempt to utilize all of the natural light. One example of these is a phase-change guest-host mode (D.L. White and G.N. Taylor, J. Appl. Phys. 45, p. 4718, 1974), which uses a cholesteric-nematic phase transition effect caused by the electric field. A reflective multicolor display using this display mode in combination with microcolor filters has also been proposed (T. Koizumi and T. Uchida, Proceedings of the SID, vol. 29, p. 157, 1988).
In the liquid crystal display device using the above display mode which does not need the polarizer, a brighter display can be obtained if the intensity of the light scattered in the direction vertical to the display screen is increased for all incident light from every direction. For this purpose, the shape of the filmed surface of a reflector for the display device should be controlled so that optimal reflective properties can be obtained. The aforementioned paper by T. Koizumi, et al. discloses a reflector which is fabricated by roughening the surface of a glass substrate with an abrasive, etching the surface with hydrofluoric acid for different periods of time thus controlling the roughness thereof and depositing a silver film on the roughened surface, so as to provide a bright reflective liquid crystal display.
However, the roughened surface of the above reflector which is formed by scratching the glass substrate with the abrasive is neither uniform in shape nor reproducible. Therefore, in the above disclosed method, it is not possible to obtain a controlled uniform reproducible surface roughness on the reflector, and thus to achieve a reflective liquid crystal display device with optimal reflective properties.
The objective of the present invention is to provide a reflective liquid crystal display device which comprises a reflector having an effective, reproducible reflective properties, and a method for fabricating such a display device.